Molecular alterations and expression of succinate dehydrogenase complex in wild-type KIT/PDGFRA/BRAF gastrointestinal stromal tumors

Abstract

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the gastrointestinal tract, disclosing somatic KIT, PDGFRA and BRAF mutations. Loss of function of succinate dehydrogenase (SDH) complex is an alternative molecular mechanism in GISTs, namely in carriers of germline mutations of the SDH complex that develop Carney-Stratakis dyad characterized by multifocal GISTs and multicentric paragangliomas (PGLs). We studied a series of 25 apparently sporadic primary wild-type (WT) KIT/PDGFRA/BRAF GISTs occurring in patients without personal or familial history of PGLs, re-evaluated clinicopathological features and analyzed molecular alterations and immunohistochemistry expression of SDH complex. As control, we used a series of well characterized 49 KIT/PDGFRA/BRAF-mutated GISTs. SDHB expression was absent in 20% and SDHB germline mutations were detected in 12% of WT GISTs. Germline SDHB mutations were significantly associated to younger age at diagnosis. A significant reduction in SDHB expression in WT GISTs was found when compared with KIT/ PDGFRA/BRAF-mutated GISTs. No significant differences were found when comparing DOG-1 and c-KIT expression in WT, SDHB-mutated and KIT/PDGFRA/BRAF-mutated GISTs. Our results confirm the occurrence of germline SDH genes mutations in isolated, apparently sporadic WT GISTs. WT KIT/PDGFRA/BRAF GISTs without SDHB or SDHA/SDHB expression may correspond to Carney-Stratakis dyad or Carney triad. Most importantly, the possibility of PGLs (Carney-Stratakis dyad) and/or pulmonary chondroma (Carney triad) should be addressed in these patients and their kindred.

Analysis of all subunits, SDHA, SDHB, SDHC, SDHD, of the succinate dehydrogenase complex in KIT/PDGFRA wild-type GIST

“…[25][26][27] More recently, somatic mutations in SDH complex were found also in KIT/PDGFRA wildtype GIST patients who, apparently, did not have personal or familial history of paraganglioma and GIST. [5][6][7][8][9][10][11][12] However, the presence of germline mutations seen in our series is interesting and should not be underestimated. At this time, it cannot be excluded that in this subset of adult KIT/PDGFRA wild-type GIST patients, without personal and family history of tumors but harboring germline mutations in SDH complex, the GIST may represent the first neoplastic event in a context of an attenuated form of CarneyStratakis syndrome or of a syndrome not yet clearly manifested and Figure 3 Western blot evaluation of SDHA and SDHB proteins.…”

“…Therefore, loss of expression of SDHB protein is supported by mutations in all SDH subunits, 4,5,[7][8][9][10][11][12] while the loss of expression of SDHA is supported only by mutations of SDHA. Results of the SDHB IHC test suggest triaging the genetic testing in SDHB, SDHC, and SDHD genes in familial pheochromocytoma/ paraganglioma; 28 as well, this may also be useful in adult nonsyndromic KIT/PDGFRA wild-type GIST with same purpose, but, we suggest adding the subunit A to the list of genetic tests since our patients with SDHA mutations were SDHB negative and the mutations in SDHA were prevalent.…”

“…4 Also, the presence of mutations on SDHB and SDHC, (which encode subunits B and C, respectively, of succinate dehydrogenase (SDH) or complex II) and, more recently, mutations on SDHA have been described separately in different reports. [5][6][7][8][9][10][11][12] Currently, the simultaneous sequencing of all subunits, A, B, C, and D of SDH complex has not been reported in a large series of clinically non-syndromic GIST that are KIT-and PDGFRA-mutation negative.…”

Low frequency of TERT promoter mutations in gastrointestinal stromal tumors (GISTs)

“…12,[18][19][20] In addition, the BRAF mutation status was evaluated in KIT/PDGFRA wild-type GISTs (n = 9) from Barretos Cancer Hospital and the SDH genes status was evaluated in KIT/PDGFRA/BRAF wildtype GISTs (n = 18) from Centro Hospitalar S. João. 15,16 Tumor genomic DNA was extracted from formalin-fixed and paraffinembedded tissues using the QIAamp DNA MicroKit (Qiagen, Hilden, Germany), following the manufacturer's instructions. 19 A fragment of the TERT promoter was amplified with PCR using primers 5′-AGTGGATTCGCG GGCACAGA-3′ and 5′-CAGCGCTGCCTGAAACTC-3′, resulting in a PCR product of 235 bp, which contained the chr5.hg19:g.1295228C4T and Chr5.…”

“…10,11 Somatic BRAF mutations [12][13][14] and germinative SDHx mutations were reported in a subset of KIT/PDGFRA wild-type GIST. 15,16 Increased telomerase activity was reported in GISTs and was associated with poor prognosis. 17 Yet, TERT promoter mutation has not been reported in GIST.…”